Method of fuel injection control

Patent metadata

Field	Value
Publication number	US-2017191442-A1
Application number	US-201614987561-A
Country	US
Kind code	A1
Filing date	Jan 4, 2016
Priority date	Jan 4, 2016
Publication date	Jul 6, 2017
Grant date	—

Abstract

Methods and systems are provided for improving engine performance at high load conditions with reduced combustion phasing while maintaining in-cylinder peak pressures within limits. Following a pilot fuel injection, a main fuel injection is split into multiple smaller injections, the smaller injections spread around a timing of the main fuel injection so that peak cylinder pressures for each injection are within cylinder pressure limits. In this way, more enthalpy is created for expediting warming of exhaust catalysts.

First claim

1 . A method for an engine, comprising:
in response to predicted peak in-cylinder pressure for a planned main fuel injection into a cylinder occurring later than a threshold timing, splitting the planned main fuel injection into at least a first and second injection, wherein the first injection is advanced relative to a timing of the planned main fuel injection.

2 . The method of claim 1 , further comprising, adjusting a timing and duration of each of the first and second injection based on a peak pressure target of the cylinder.

3 . The method of claim 2 , wherein the adjusting based on a peak pressure limit of the cylinderncludes adjusting based on an output of an in-cylinder pressure sensor relative to the peak pressure target.

4 . The method of claim 2 , wherein the adjusting includes, advancing the timing of the first injection relative to the timing of the planned main fuel injection to maintain a peak in-cylinder pressure of the first injection at or below the peak pressure target.

5 . The method of claim 4 , ending a duration of the first injection when the peak in-cylinder pressure of the first injection reaches the peak pressure target.

6 . The method of claim 4 , wherein the adjusting further includes retarding the timing of the second injection relative to the timing of the first injection to maintain a peak in-cylinder pressure of the second injection at or below the peak pressure target.

7 . The method of claim 2 , wherein the engine is a boosted engine including an intake compressor driven by an exhaust turbine, and wherein the duration of the second injection is further adjusted based on an inlet temperature of the turbine, the duration decreased as the turbine inlet temperature increases above a threshold temperature.

8 . The method of claim 2 , wherein the timing and duration of each of the first and second injection is further adjusted based on an estimated BSFC of the engine.

9 . The method of claim 1 , wherein the planned main fuel injection is a main injection following a pilot fuel injection, and where the cylinder pressure has only two peaks, each peak corresponding to one of the two main injections, and where the two peaks are within a threshold of each other including within 10% of each other but both below a maximum allowable cylinder pressure determined based on engine operating conditions.

10 . The method of claim 9 , wherein while splitting the planned main fuel injection, a timing and duration of the pilot fuel injection is maintained.

11 . A method for an engine, comprising:
operating an engine with combustion timing at a target timing and a lower EGR rate until a first, upstream exhaust catalyst is higher than a threshold temperature; and then, operating the engine with combustion timing retarded from the target timing and a higher EGR rate to expedite heating of a second, downstream exhaust catalyst, the retarded combustion timing including a split fuel injection.

12 . The method of claim 11 , wherein operating the engine with combustion timing retarded from the target timing includes splitting a planned main fuel injection into at least a first and second injection, wherein a timing of the first injection is calibrated based on operator torque demand and wherein a timing of the second injection is retarded relative to the timing of the first injection, and wherein an injection amount of the second injection is based on exhaust temperature.

13 . The method of claim 12 , wherein each of the lower EGR. rate and the higher EGR rate are adjusted based on each of an age of the first and second catalyst, an engine temperature, and an exhaust temperature.

14 . The method of claim 12 , wherein a duration between an end of the first injection and a start of the second injection is adjusted based on a temperature of the second catalyst.

15 . The method of claim 12 , wherein the engine is a turbocharged engine and wherein a duration of the second injection is adjusted based on one or more of a turbine inlet temperature, exhaust NOx level, exhaust tailpipe hydrocarbon level, and exhaust CO level.

16 . A method for a boosted engine, comprising:
during a first condition, splitting a fuel injection and advancing an average combustion timing of the split fuel injection based on peak cylinder pressure and turbine inlet temperature; and during a second condition, splitting the fuel injection and retarding the average combustion timing of the split fuel injection based on catalyst temperature.

17 . The method of claim 16 , wherein splitting the fuel injection includes splitting a planned main fuel injection following a pilot injection of a combustion cycle, wherein during the first condition, the average combustion timing of the split fuel injection is advanced relative to a combustion timing of the planned main fuel injection, and wherein during the second condition, the average combustion timing of the split fuel injection is retarded relative to the combustion timing of the planned main fuel injection.

18 . The method of claim 17 , wherein during the first condition, the splitting includes splitting the fuel injection into at least a first injection advanced from the combustion timing of the planned main fuel injection and at least a second injection retarded from the combustion timing of the planned main fuel injection, a duration of the first injection and a duration between the first injection and the second injection adjusted based on estimated peak cylinder pressure relative to a cylinder pressure limit, a duration of the second injection adjusted based on the turbine inlet temperature.

19 . The method of claim 17 , wherein during the second condition, the splitting includes splitting the fuel injection into at least a first injection advanced or retarded from the combustion timing of the planned main fuel injection and at least a second injection retarded from the combustion timing of the first injection, the first injection based on engine load, the second injection based on the catalyst temperature.

20 . The method of claim 19 , wherein the engine includes each of a first upstream exhaust catalyst and a second downstream exhaust catalyst coupled to an engine exhaust manifold, and wherein during the first condition, each of the first and second exhaust catalysts have achieved light-off, and wherein during the second condition, an amount of fuel in the second injection is limited when the first exhaust catalyst has not achieved light-off, and wherein the amount of fuel in the second injection is increased after the first exhaust catalyst has achieved light-off, the amount increased to light-off the second exhaust catalyst.

Assignees

• Ford Global Tech Llc

Inventors

• Polonowski Christopher
• Kurtz Eric Matthew
• Lauri Andrew
• Van Nieuwstadt Michiel J
• Tennison Paul Joseph
• Finchum Jonathan

Classifications

• Y02T10/40

  Engine management systems · CPC title

• F02D41/3076

  with special conditions for selecting a mode of combustion, e.g. for starting, for diagnosing · CPC title

• F02D41/403 Primary

  with pilot injections · CPC title

• F02D41/064

  at cold start (F02D41/067 takes precedence) · CPC title

• F02D41/068

  for warming-up · CPC title